Coffee or milk machine and method of operating such a machine

Abstract

A coffee machine including a frother with an outlet channel for coffee and milk foam, and supply channels for milk, air, and steam respectively, and a nonreturn valve to prevent a fluid in one of the channels from flowing in an undesirable direction. The coffee machine also includes a clean water supply channel that connects to the milk supply channel with a T-junction distant from the frother. The T-junction further connects to a source channel for the milk.

What is claimed is: 
     
       1. A machine comprising:
 a frother comprising an outlet channel for milk foam, and supply channels for milk, steam, and air respectively, and comprising a nonreturn valve to prevent a fluid in one of the channels from flowing in an undesirable direction; 
 a clean water supply channel that connects to the milk supply channel with a T-junction distant from the frother, wherein the T-junction further connects to a source channel for the milk, and wherein the clean water supply channel and the milk supply channel comprise a tube in tube construction. 
 
     
     
       2. The machine of  claim 1 , wherein the clean water supply channel comprises a control valve connected to a controller which is arranged to cause that a burst of clean water is introduced into the milk supply channel immediately before milk enters the milk supply channel coming from the source channel for the milk. 
     
     
       3. The machine of  claim 1 , wherein the T-junction comprises the nonreturn valve to prevent that clean water from the clean water supply channel enters the source channel for the milk. 
     
     
       4. The machine of  claim 3 , wherein the nonreturn valve is of the duckbill type. 
     
     
       5. The machine of  claim 1 , wherein at least one of the milk supply channel and the source channel for the milk is provided with an internal coating with hydrophobic and/or oleophobic properties. 
     
     
       6. The machine of  claim 5 , wherein the coating comprises nanoparticles of silver or silver compounds. 
     
     
       7. The machine of  claim 6 , wherein the nanoparticles have a dimension between about 10 −10  and about 10 −7  m. 
     
     
       8. The machine according to  claim 1 , wherein the machine is a coffee machine. 
     
     
       9. A method of operating a machine according to  claim 1 , comprising the step of, at the start of operating the frother, initially bursting a temporary burst of water supplied by the clean water supply channel guided in and through the milk supply channel towards the frother. 
     
     
       10. The method according to  claim 9 , wherein the initial temporary burst of water is applied for a duration of between about 0.01 and about 3 seconds. 
     
     
       11. The method according to  claim 10 , wherein the initial temporary burst of water is applied for a duration of between about 0.05 and about 0.15 seconds. 
     
     
       12. The method according to  claim 9 , further comprising the step of, after operating the frother, guiding clean water through the milk supply channel, the frother and the outlet channel, wherein the clean water is supplied by the clean water supply channel. 
     
     
       13. The method according to  claim 9 , further comprising the step of placing a container with cleaning agent in fluid communication with the source channel for the milk, at repeated intervals, so as to rinse and clean the machine. 
     
     
       14. The method according to  claim 13 , wherein the cleaning agent is both a descalant to remove limescale and a microbicidal to destroy microbes. 
     
     
       15. The method according to  claim 13 , wherein the cleaning agent is an acid descalant and microbicidal, comprising about 50-150 ppm peracetic acid. 
     
     
       16. The machine of  claim 6 , wherein the nanoparticles have a dimension in the range of about 1-100 nm. 
     
     
       17. The machine of  claim 6 , wherein the nanoparticles have a dimension in the range of about 10-60 nm.